MEMS Comb Electrode Structure for Lower Parasitic Capacitance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing MEMS structure with a large opposing surface area between the fixed electrode and the base results in significant parasitic capacitance, affecting the efficiency of voltage extraction in vibration-driven energy harvesting devices.
Innovation Solution
The MEMS element design includes a base with a projecting portion and a comb tooth linking portion, where the base is partially removed to create a gap between the projecting portion and the comb tooth linking portion, reducing the opposing surface area and thereby minimizing parasitic capacitance. Additionally, the fixed electrode pads and lead portions are only partially fixed to the base, further reducing capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the fixed electrode is formed as an integrated part with the base and fixed over a large area, then the structural stability and ease of manufacture are improved, but the parasitic capacitance between the fixed electrode and the base increases significantly
Solution Approach 1:
The patent extracts and removes portions of the base that would otherwise face opposite the fixed electrode. Specifically, the base has openings formed therein, and portions of the base are removed to create gaps between the fixed electrode and the remaining base structure. This extraction of base material eliminates the source of parasitic capacitance while maintaining the structural integrity of the device through the remaining base portions that provide support and anchoring for the electrodes.
Solution Approach 2:
The patent segments the base structure by creating multiple openings and removing specific portions, transforming the base from a continuous solid structure into a segmented structure with strategic gaps. This segmentation allows the fixed electrode to be positioned over the openings without facing opposite continuous base material, thereby reducing parasitic capacitance while still maintaining structural stability through the remaining base segments.
2Strength
If the fixed electrode and base face opposite each other over a large area, then the structural support is improved, but the parasitic capacitance increases
Solution Approach 1:
The patent applies the extraction principle by removing specific portions of the base that would create large opposing surfaces with the fixed electrode. The openings and gaps are strategically positioned to eliminate parasitic capacitance sources while preserving the structural support function through the remaining base material that continues to provide anchoring and mechanical stability.
Solution Approach 2:
The patent applies local quality by creating non-uniform base structure with specific portions removed rather than uniformly thinning the entire base. The base maintains full thickness and structural integrity in critical support areas while having portions removed in regions that would create parasitic capacitance, thereby providing different local properties (full structural support vs. reduced capacitance) in different spatial locations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively reduces parasitic capacitance, enhancing the efficiency of voltage extraction and power output in vibration-driven energy harvesting devices by minimizing electric charge accumulation between the base and the electrodes.
Implementation Method 1
a movable electrode having a plurality of movable comb teeth which are interdigitated with the fixed comb teeth
Implementation Method 2
an electret layer formed in the device layer
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A MEMS element includes: a base; a fixed electrode having a plurality of fixed comb teeth, a fixed electrode pad and a support fastening portion; and a movable electrode having a plurality of movable comb teeth which are interdigitated with the fixed comb teeth, wherein: the support fastening portion includes a comb tooth linking portion that links the plurality of fixed comb teeth; and a portion of the base, which would face opposite at least part of the comb tooth linking portion over an entire length running along a direction perpendicular to a direction in which the plurality of fixed comb teeth are set one after another, is removed.